Alnylam Plunges 42% After Ending Development of a Key Medicine

  • More patients died on drug than those on placebo, company says
  • Alnylam says decision doesn’t affect other lead program

Alnylam Pharmaceuticals Inc. plunged in trading before U.S. exchanges opened after ending development of its late-stage experimental drug for a rare disease because of safety concerns.

More patients taking the drug were dying compared to those getting a placebo, the company said in a statement after the market closed Wednesday. The treatment, revusiran, was being tested for a condition called hereditary ATTR amyloidosis with cardiomyopathy, which can lead to nerve and heart damage.

“We’re very sad to report the outcome here,” Akshay Vaishnaw, Alnylam’s chief medical officer, said on a call with investors. “In terms of causality, we don’t have an explanation for this finding.”

The shares fell 42 percent to $40.65 at 6:45 a.m. New York time, cutting the value of the company’s $6.03 billion market capitalization by almost half.

The decision to halt the trial was made after reports of new or worsening nerve damage in another study of the drug, which caused Alnylam to ask an independent committee overseeing the trial to make an assessment. The committee concluded that the drug’s benefits were not worth its risks, and the company subsequently found that more patients taking revusiran had died than those on placebo.

Eighteen Deaths

Of the 206 people in the study, 18 died, mostly because of heart-related issues, Vaishnaw said on the call. He declined to give a breakdown of how many of those deaths were among patients on the drug, but said none of the deaths were classified as drug-related.

Christine Lindenboom, an Alnylam spokeswoman, declined to provide more details on the patient deaths. “We just learned of the imbalance of mortality today,” she said in an e-mail. “We now need to take the time to go back and analyze the root cause of this observation.”

The Medicines Co., which is testing a heart-disease therapy that uses Alnylam technology, slid 12 percent after markets closed. The drugmaker said Wednesday that it had seen no particular safety issues with the drug, known as PCSK9si, in a mid-stage study. Arrowhead Pharmaceuticals Inc., which uses an approach similar to Alnylam’s, fell 3.7 percent.

Revusiran is one of two drugs Alnylam has in final-stage trials. The other, patisiran, is a related medicine for a similar condition called hereditary ATTR amylydosis with polyneuropathy. The decision to stop developing revusiran doesn’t affect patisiran, Alnylam said. Analysts had expected revusiran to reach more than $1 billion in sales by 2023, according to an average of five analyst estimates compiled by Bloomberg.

Alnylam’s drugs use a technology known as RNA interference, or RNAi. It works by turning off specific sections of RNA that act as instructions to make proteins, thereby stopping the formation of disease-causing proteins. In ATTR amyloidosis, malformed proteins accumulate in the heart and peripheral nerves, causing damage.

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